The present invention relates to the field of brushes and more particularly to such brushes wherein the bristle tufts are fused to the brush base.
Brushes have been made by the process of fusing, or thermal welding parts made of thermoplastic polymers, for many years. In this process, the brush base is mounted in a jig and bristles are acquired by picking tubes from a magazine hopper to form tufts. The fusing process involves melting a number of tuft receptor sites in the form of discrete cavities into a surface of the brush base, melting an attachment end of an equal number of tufts of bristles, and quickly inserting the melted tuft ends into the cavities so that the melted tuft ends are pressed into the melted cavities. When the melted resin has flowed together and cooled, the components are permanently welded together. This conventional method of fusing bristles to a brush base is confined to the case in which the two components, the brush base and the bristles, are formed of resins from the same polymer family in order to achieve proper adherence. This similar polymer limitation exists because of the well accepted principle that dissimilar polymers do not weld to one another.
However, the present invention recognizes that a polymer that is chosen for extruding bristles may not be the best choice for a brush base. For example, a polymer chosen for its properties of bristle toughness and flexibility may impose on a brush base a higher resin cost, a higher expense for the molding of a brush base, or inferior properties than would be the case with a polymer chosen initially to mold a brush base. If the brush maker were able to employ bristles of a polymer chosen for its extrusion properties of toughness and flexibility and a base of a polymer chosen for its stability and cost, efficiency, appearance, economy, and other factors would be improved. The invention further recognizes that a resin with dispersed particles or fibers provides a stable, efficient, and economical material from which a brush based could be made, whether the bristles are made of a similar or dissimilar material.
Therefore, it is an object of the present invention to provide a fused brush in which the bristles and the brush base are made of different polymers.
It is a further object of the present invention to provide a fused brush in which the fusion attachment is substantially permanent.
It is an additional object of the present invention to provide a fused brush in which the brush base contains dispersed particles.
It is a still further object of the present invention to provide a fused brush in which the brush base contains dispersed particles and the bristles are of a polymer that is the same as, or different than, the polymer of which the brush base is formed.
These and other objects of the present invention will become apparent through the disclosure of the invention to follow.
The present invention provides a fused brush and method of making in which the bristles are formed of a first polymer and the base is formed of the same or another polymer. In one preferred embodiment, the brush base is a molded, thermoformed, or extruded block form. The resin forming the block contains dispersed particles of the type generally used for reinforcing polymer rigidity. The brush block is prepared for bristle attachment by pressing a set of heated protuberances into an attachment surface of the block to form cavities with portions of the dispersed particles exposed. Attachment ends of the bristles are softened by contact with a heated surface. The softened bristle ends are then pressed into the melted cavities. It has been discovered that, upon cooling, the particles of the brush block have mechanically engaged the melted ends of the bristles to permanently, mechanically anchor the bristle tufts to the brush block. In brushes having bristles made of the same polymer as that of the brush block, the mechanical grip enhances the weld of the resin fusion.
In a further embodiment in which the base is a woven or looped mat, the bristle tuft ends are melted and the mat either remains cool or is partly melted. When the melted tuft ends are pressed into the mat, the molten polymer flows around the mat fibers and, upon cooling, are permanently, mechanically anchored thereto.